Release v1.3.0

What's Changed

Add comprehensive test suite and migrate to isolated worker model:
- Add 73 comprehensive tests covering core functionality
- Migrate from in-process to isolated worker model
- Worker Runtime: dotnet-isolated (changed from dotnet)
- .NET Version: 6.0 (unchanged)
- No breaking changes: backward compatible with existing data
by @adthom in #83

Full Changelog: 1.2...v1.3.0